Modern low-voltage circuit breakers are equipped with an electronic tripping device, and contain a programmable microcontroller. The tripping device can be used for a plurality of low-voltage circuit breakers with different ratings, and can be matched to the respective circuit breaker type. For this purpose, the tripping device requires type data as well as other individual data items about the circuit breaker, that is to say calibration data describing specific hardware data, calibration data for analog measurement inputs of the microcontroller, as well as the serial number and identification number of the circuit breaker, by means of which each individual breaker can be identified. This data should be stored as safely and invariably as possible.
One normal solution is for this data to be stored in a rewritable information memory, for example flash-EEPROM, or a serial EEPROM, and to be read by the software as required. The linking process between them often involves slow serial data buses such as I2C or SPI. This reading process has a negative influence on the time taken for complete activation.
DE 198 45 799 A1 discloses the information memory being integrated in the plug-in apparatus of a connecting line between a current transformer and an overcurrent release.
Since this requires a special plug, DE 100 19 092 A1 has proposed for an EEPROM to be inserted directly in the connecting line. Since the connecting line is subject to the interference influence of electrical fields in the circuit breaker, DE 102 21 572 A1 has proposed that the information memory be accommodated physically separately from the overcurrent release in the circuit breaker, and that it be operated by means of a write protection system. The write protection can be activated either via the overcurrent release and a data bus, or via a special programmer (DE 102 21 579 A1). According to DE 102 21 571 A1, activation and deactivation are possible by varying the supply voltage, for example changing the polarity of the supply voltage to the information memory.
The information memory with a write protection system has the disadvantage that the writing/reading cycle can be influenced by electromagnetic interference fields, and that data losses can occur in the event of an inadvertent change from the read mode to the write mode.